Do Language Models Reason Across Languages?

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Hauptverfasser: Meng, Yan, Mohammed, Wafaa, Monz, Christof
Format: Preprint
Veröffentlicht: 2026
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author Meng, Yan
Mohammed, Wafaa
Monz, Christof
author_facet Meng, Yan
Mohammed, Wafaa
Monz, Christof
contents The real-world information sources are inherently multilingual, which naturally raises a question about whether language models can synthesize information across languages. In this paper, we introduce a simple two-hop question answering setting, where answering a question requires making inferences over two multilingual documents. We find that language models are more sensitive to language variation in answer-span documents than in those providing bridging information, despite the equal importance of both documents for answering a question. Under a step-by-step sub-question evaluation, we further show that in up to 33% of multilingual cases, models fail to infer the bridging information in the first step yet still answer the overall question correctly. This indicates that reasoning in language models, especially in multilingual settings, does not follow a faithful step-by-step decomposition. Subsequently, we show that the absence of reasoning decomposition leads to around 18% composition failure, where both sub-questions are answered correctly but fail for the final two-hop questions. To mitigate this, we propose a simple three-stage SUBQ prompting method to guide the multi-step reasoning with sub-questions, which boosts accuracy from 10.1% to 66.5%.
format Preprint
id arxiv_https___arxiv_org_abs_2601_06644
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Do Language Models Reason Across Languages?
Meng, Yan
Mohammed, Wafaa
Monz, Christof
Computation and Language
Artificial Intelligence
The real-world information sources are inherently multilingual, which naturally raises a question about whether language models can synthesize information across languages. In this paper, we introduce a simple two-hop question answering setting, where answering a question requires making inferences over two multilingual documents. We find that language models are more sensitive to language variation in answer-span documents than in those providing bridging information, despite the equal importance of both documents for answering a question. Under a step-by-step sub-question evaluation, we further show that in up to 33% of multilingual cases, models fail to infer the bridging information in the first step yet still answer the overall question correctly. This indicates that reasoning in language models, especially in multilingual settings, does not follow a faithful step-by-step decomposition. Subsequently, we show that the absence of reasoning decomposition leads to around 18% composition failure, where both sub-questions are answered correctly but fail for the final two-hop questions. To mitigate this, we propose a simple three-stage SUBQ prompting method to guide the multi-step reasoning with sub-questions, which boosts accuracy from 10.1% to 66.5%.
title Do Language Models Reason Across Languages?
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2601.06644